1. Field of the Invention
The present invention is directed to recycling articles that include high-performance fiber into yarns and articles made therefrom.
2. Description of the Related Art
Fabrics that include high-performance fibers such as aramid fiber are well-known in the art. These fabrics may be used in a wide variety of articles to increase the ballistic resistance or cut and abrasion resistance of those articles. Examples of such articles are bullet resistant vests, gloves, chaps, and the like.
U.S. Pat. No. 6,103,646 discloses a penetration resistant ballistic article which includes an outer face made from a plurality of tightly woven layers of aramid yarns and an inner face of a plurality of layers of ballistic resistant fibrous material such as aramid yarns.
U.S. Pat. No. 5,876,834 discloses protective chain saw chaps made from a fabric of aramid yarns.
Fabrics that include high-performance fibers or yarns are used to make many other articles, such as cut-resistant gloves and the like.
A problem with articles made from fabric that includes high-performance fiber is how to dispose of such articles. Articles such as ballistic resistant vests usually have a useful life of 5 to 10 years, after which time the vests must be replaced, which raises the issue of how to dispose of the worn vests. There is an ongoing need to reduce waste through recycling. The general concept of recycling waste fabric is known. See for example U.S. Pat. No. 5,369,861 which discloses a process for recycling denim waste. A continuing need exists for new and improved recycling processes.
The present invention is directed to a process for recycling a fabric, which fabric includes high performance fibers having a tenacity of at least 10 grams per dtex and a tensile modulus of at least 150 grams per dtex, to make a yarn from the fabric. In the process, a fabric is provided that includes fibers having a tenacity of at least 10 grams per dtex and a tensile modulus of at least 150 grams per dtex, and the fabric is cut into pieces no dimension larger than 15 centimeters. From 30 to 99 weight percent staple fibers on a basis of staple fibers and high performance fibers are added to the fabric pieces to make a blend and the fibers of the blend are separated and aligned into a sliver, and the sliver is formed into a twisted yarn. This yarn may be used to make a fabric or any other useful article. Additional fibers may be present in the yarn.
The present invention is directed to recycling articles that include high-performance fiber to make a yarn that may be used to make other articles.
Articles that include high-performance fibers or high performance yarns, which are typically present in the form of continuous multifilament yarns, have many uses, including bullet resistant vests, cut resistant gloves, chaps, and the like. In the process of the invention, the article that incorporates a fabric having high-performance fiber is disassembled or taken apart so as to provide the fabric without any covering, stitching or the like. For example, a bullet resistant vest typically includes a plurality of fabric layers stitched together that are usually covered by a shell or other covering fabric. The outer shell or covering fabric is removed to reveal the plurality of fabric layers, and the stitching of the fabric layers is removed so that what is left is only the fabric sheets that include high-performance fiber. Some stitching may remain in the fabric but is usually not desirable because the stitching leads to a yarn of a lower quality.
Articles and fabrics of the present invention are made, in whole or in part, from yarns that include high performance fibers. As used herein, the term xe2x80x9chigh performance fibersxe2x80x9d means fibers having a tenacity of at least 10 grams per dtex and a tensile modulus of at least 150 grams per dtex. Such yarns can be made from fibers such as aramids, polyolefins, polybenzoxazole, polybenzothiazole, and the like, and may be made from mixtures of such yarns.
The fabric may include up to 100 percent aramid fiber. By xe2x80x9caramidxe2x80x9d is meant a polyamide wherein at least 85% of the amide (xe2x80x94COxe2x80x94NHxe2x80x94) linkages are attached directly to two aromatic rings. Examples of aramid fibers are described in Man-Made Fibersxe2x80x94Science and Technology, Volume 2, Section titled Fiber-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers are, also, disclosed in U.S. Pat. Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3,354,127; and 3,094,511.
Para-aramids are common polymers in aramid yarn and poly(p-phenylene terephthalamide)(PPD-T) is a common para-aramid. By PPD-T is meant the homopolymer resulting from mole-for-mole polymerization of p-phenylene diamine and terephthaloyl chloride and, also, copolymers resulting from incorporation of small amounts of other diamines with the p-phenylene diamine and of small amounts of other diacid chlorides with the terephthaloyl chloride. As a general rule, other diamines and other diacid chlorides can be used in amounts up to as much as 10 mole percent of the p-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher, provided only that the other diamines and diacid chlorides have no reactive groups which interfere with the polymerization reaction. PPD-T, also, means copolymers resulting from incorporation of other aromatic diamines and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride or 3,4xe2x80x2-diaminodiphenylether. For the purposes of this invention, para-aramid also includes highly modified wholly aromatic copolyamides such as copoly(p-phenylene/3,4xe2x80x2-diphenyl ether terephthalamide).
By xe2x80x9cpolyolefinxe2x80x9d is meant polyethylene or polypropylene. By polyethylene is meant a predominantly linear polyethylene material of preferably more than one million molecular weight that may contain minor amounts of chain branching or comonomers not exceeding 5 modifying units per 100 main chain carbon atoms, and that may also contain admixed therewith not more than 50 weight percent of one or more polymeric additives such as alkene-1-polymers, in particular low density polyethylene, propylene, and the like, or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening agents, colorants and the like which are commonly incorporated. Such is commonly known as extended chain polyethylene (ECPE). Similarly, polypropylene is a predominantly linear polypropylene material of preferably more than one million molecular weight. High molecular weight linear polyolefin fibers are commercially available.
Polybenzoxazole and polybenzothiazole are preferably made up of polymers of the following structures: 
While the aromatic groups shown joined to the nitrogen atoms may be heterocyclic, they are preferably carbocyclic; and while they may be fused or unfused polycyclic systems, they are preferably single six-membered rings. While the group shown in the main chain of the bis-azoles is the preferred para-phenylene group, that group may be replaced by any divalent organic group which does not interfere with preparation of the polymer, or no group at all. For example, that group may be aliphatic up to twelve carbon atoms, tolylene, biphenylene, bis-phenylene ether, and the like.
The fabric is then cut into relatively small pieces, preferably with a largest dimension no longer than fifteen centimeters (six inches) and more preferably no longer than five centimeters (two inches). Pieces of cut fabric which are longer than fifteen centimeters (six inches) are typically removed because those longer pieces have the potential to cause problems when that cut fabric is made into a yarn. For short staple processing, pieces of cut fabrics which have a largest dimension greater than five centimeters (two inches) are typically removed. It is understood that in the present invention a maximum size of the cut fabric will be dependent on later process steps in making a yarn. Illustratively, smaller fabric pieces will be employed in a short staple (cotton) system of manufacture compared to other known techniques of yarn formation used for long staple (woolen or worsted systems).
A preferred means of cutting the fabric is by use of guillotine cutters which cut a number of different angles. A typical guillotine cutter will cut at six different angles. While a guillotine cutter is preferred, the selection of a cutting device is not critical to the invention provided the fabric is cut into pieces of the correct size.
The pieces of cut fabric are blended with 30 to 99, and preferably 50 to 95, weight percent staple fibers on the basis of the staple fibers in combination with the high performance fibers in the cut yarn. As used herein, xe2x80x9cstaple fibersxe2x80x9d means any natural or synthetic fibers having a length of no greater than 15 centimeters with the proviso that the staple fibers differ from the composition of the high performance fibers. Therefore the purpose of this disclosure the staple fiber could also be a high performance fiber provided it is a composition which differs from the high performance fiber of the cut fabric pieces.
Also it is understood that in the present invention additional virgin, i.e., non-recycled high performance fiber may be added in manufacture of the yarn. The virgin high performance fiber may be present to facilitate processing. Illustratively, equal amounts of recycled high performance fiber in the cut fabric and virgin high performance fiber may be employed
Examples of suitable staple fibers include cotton, wool, polyester, polyamide, rayon and mixtures thereof as well as the high performance fibers listed above. Also other fibers may be included, e.g. for anti-static properties. Suitable anti-static properties are described, for example, in U.S. Pat. No. 3,803,453 and U.S. Pat. No. 4,612,150.
This blend is then formed into a sliver. A preferred method for forming the blend into a sliver is with a carding machine, a machine commonly used in the fiber industry to separate, align, and deliver fibers into a continuous strand of loosely assembled fibers without twist, commonly known as a sliver.
When the cut pieces of fabric are processed through a carding machine, the card separates the individual fibers in the fabric and the recycled fibers along with any other fibers in the blend are formed into a wispy web, which is conventionally made into a sliver of one inch diameter. The sliver is then made into a roving through a conventional drawing process and then typically formed into a twisted yarn using any common method for making spun yarns, e.g. a ring-spinning machine.
Alternatively, the sliver may be spun directly to a yarn, using for example an open-end spinning machine an example of which is a Murata jet air spinner, or a core-spinning machine, an example of which is a DREF friction spinner.
There is no limitation on the types or size of yarns that may be made according to the process of the invention. However, this process is especially suited for providing staple yarns having a singles yarn count of 8.5 numbers metric (about an English cotton count of 5) or finer, and preferably yarns having a singles yarn count of 8.5 to 34 numbers metric (about 5 to 20 English cotton count). These single yarns can also be combined to form plied yarns.
The yarn that includes the recycled high-performance fiber may be used to make fabrics in a conventional manner. Such fabrics may include any amount of the recycled yarn. A fabric made using the yarn made from this invention may be used in any other article into which yarn containing high-performance fiber is used, such as tents, gloves, chaps, helmets, clothing, and the like.